368 ME. A. DOEAN ON THE 



brium in this specimen from the American skeleton is l'9centim., 

 nearly 1 centim. less than in the 'Yega' malleus. In other 

 respects the mallei from the two specimens are very similar. 



In my mouograph, when describing tlie manubrium oiManatus, 

 I wrote : — " The upper border is very sharp and narrow ; it forms 

 a semicircle, and projects against the membraua tympani in the 

 live subject ; the outer border is short, and its margins, united 

 above, diverge but little towards the extremity ; its surface is 

 concave vertically, and slightly convex horizontally "*. 



Careful examination and comparison of the manubrium in all 

 three genera lead me to believe that what I termed the upper 

 border in the manubrium of Manatus is in reality only the upper 

 part of the outer border. A small projection where this border 

 joins the body of the malleus above represents a suppressed 

 upper border. What I termed the outer border is, properly 

 speaking, only its spatulate termination, sharply deflected from 

 the superior portion of the same border. 



The upper border of the manubrium, then, is obsolete in Ma- 

 natus. In Halicore " it is very broad .... and sharply bordered 

 from the sides ; externally it runs into the outer aspect by form- 

 ing a prominent bold convexity instead of a j)rocessus brevis "t. 

 In Bhytina the upper border of the manubrium is quite distinct, 

 running for nearly half a centimeter from the body of the malleus 

 to the outer border, from which it is separated by a very distinct 

 " processus brevis." This in itself gives the malleus of JRliytina 

 a far more generalized character than can be detected either in 

 Manatus or in Salicore. It is a distinct approach in form to the 

 long scythe-like manubrium of many ruminants. 



Eeturuing to the body of the malleus, it appears even bulkier 

 than in Manatus. It bulges more posteriorly than forwards, 

 whilst in the Manatee the anterior projection is greater, as the 

 appended measurements will show. The processus gracilis is 

 much stouter than in Manatus. The articulated surfaces are 

 very deep, and of the Manatus type %. The incus is as in Ma- 

 natus, the body is equally shallow and wide, and the crura are 

 very divergent. This bone occupies the same position to the 

 malleus as seen in the other Sirenia. 



The following measurements will give some idea of the bulk of 



* Loc. cit. p. 468. t Loc. cit. p. 466. 



\ There is no peg-like process below the superior facet, like that which I have 

 seen in Manatus americanus, but never found in M. senegalensis. 



